A triple GEM detector with two dimensional readout

The triple GEM detector is a micropattern gas detector which consists of a primary ionisation gap and three consecutive gas electron multiplier (GEM) foils. A printed circuit board with readout strips detects the current induced by the drifting electron cloud originating from the last GEM stage. Thus the gas amplification and the signal readout are completely separated. Triple GEM detectors are being developed as a possible technology for the inner tracking in the LHCb experiment. In an earlier note we have reported first experience with such a detector in a test beam at PSI. Here we describe the construction of an improved version (thinner transfer gaps, segmented GEM foils, two dimensional readout). Results from performance measurements are presented using intense hadronic beams as well as cosmic ray data.Comment: 20 pages, 24 figure

Pulsation of Spherically Symmetric Systems in General Relativity

The pulsation equations for spherically symmetric black hole and soliton solutions are brought into a standard form. The formulae apply to a large class of field theoretical matter models and can easily be worked out for specific examples. The close relation to the energy principle in terms of the second variation of the Schwarzschild mass is also established. The use of the general expressions is illustrated for the Einstein-Yang-Mills and the Einstein-Skyrme system.Comment: 21 pages, latex, no figure

Instability Proof for Einstein-Yang-Mills Solitons and Black Holes with Arbitrary Gauge Groups

We prove that static, spherically symmetric, asymptotically flat soliton and black hole solutions of the Einstein-Yang-Mills equations are unstable for arbitrary gauge groups, at least for the ``generic" case. This conclusion is derived without explicit knowledge of the possible equilibrium solutions.Comment: 26 pages, LATEX, no figure

Remark on formation of colored black holes via fine tuning

In a recent paper (gr-qc/9903081) Choptuik, Hirschmann, and Marsa have discovered the scaling law for the lifetime of an intermediate attractor in the formation of n=1 colored black holes via fine tuning. We show that their result is in agreement with the prediction of linear perturbation analysis. We also briefly comment on the dependence of the mass gap across the threshold on the radius of the event horizon.Comment: 2 pages, RevTex, 2 postscript figure

Weak-field limit of Kaluza-Klein models with spherical compactification: experimental constraints

We investigate the classical gravitational tests for the six-dimensional Kaluza-Klein model with spherical (of a radius $a$) compactification of the internal space. The model contains also a bare multidimensional cosmological constant $\Lambda_6$. The matter, which corresponds to this ansatz, can be simulated by a perfect fluid with the vacuum equation of state in the external space and an arbitrary equation of state with the parameter $\omega_1$ in the internal space. For example, $\omega_1=1$ and $\omega_1=2$ correspond to the monopole two-forms and the Casimir effect, respectively. In the particular case $\Lambda_6=0$, the parameter $\omega_1$ is also absent: $\omega_1=0$. In the weak-field approximation, we perturb the background ansatz by a point-like mass. We demonstrate that in the case $\omega_1>0$ the perturbed metric coefficients have the Yukawa type corrections with respect to the usual Newtonian gravitational potential. The inverse square law experiments restrict the parameters of the model: $a/\sqrt{\omega_1}\lesssim 6\times10^{-3}\ {{cm}}$. Therefore, in the Solar system the parameterized post-Newtonian parameter$\gamma$is equal to 1 with very high accuracy. Thus, our model satisfies the gravitational experiments (the deflection of light and the time delay of radar echoes) at the same level of accuracy as General Relativity. We demonstrate also that our background matter provides the stable compactification of the internal space in the case$\omega_1>0$. However, if$\omega_1=0$, then the parameterized post-Newtonian parameter$\gamma=1/3$, which strongly contradicts the observations.Comment: 8 pages, no figures, revised version, equations and references added, accepted for publication in Phys. Rev. D. arXiv admin note: significant text overlap with arXiv:1107.338

Rotating solitons and non-rotating, non-static black holes

It is shown that the non-Abelian black hole solutions have stationary generalizations which are parameterized by their angular momentum and electric Yang-Mills charge. In particular, there exists a non-static class of stationary black holes with vanishing angular momentum. It is also argued that the particle-like Bartnik-McKinnon solutions admit slowly rotating, globally regular excitations. In agreement with the non-Abelian version of the staticity theorem, these non-static soliton excitations carry electric charge, although their non-rotating limit is neutral.Comment: 5 pages, REVTe

O(4) texture with a cosmological constant

We investigate O(4) textures in a background with a positive cosmological constant. We find static solutions which co-move with the expanding background. There exists a solution in which the scalar field is regular at the horizon. This solution has a noninteger winding number smaller than one. There also exist solutions in which scalar-field derivatives are singular at the horizon. Such solutions can complete one winding within the horizon. If the winding number is larger than some critical value, static solutions including the regular one are unstable under perturbations.Comment: 25 pages, revtex, 6 eps figure